The DataRow need to be created before adding it to the DataRow collection.
For instance,
DataTable dt = new DataTable();
dt.Columns.Add("ID");
dt.Columns.Add("Name");
var dr = dt.NewRow();
dr[0] = "1";
dr[1] = "AAA";
dt.Rows.Add(dr);
... likewise
foreach (DataRow dr in dt.Rows)
{
obj.Add(dr);
}
Now the List should hold the Rows. Let me know if it works.